• by Kirk Gaw

Walkerton Scientist - Dr. Harold C. Urey - Early Beginnings - Heavy Hydrogen and NASA

Dr. Harold C. Urey, 1934 Nobel prize winner for his discovery of heavy hydrogen and considered Father of NASA was born in Walkerton on April 29, 1893. His father was a minister at the Walkerton Church of the Brethren, teacher, and superintendent of Walkerton schools at that time. After his father Reverend Samuel passed away when Harold was 6, his Mom Cora Reinoehl moved to nearby Kendallville east of Walkerton where he attended school. That didn’t stop Harold from visiting his Grandparents who continued to live in Walkerton? Upon graduation from grade school at age fourteen, Urey barely managed to pass the entrance exams for high school. But in high school he became interested in all aspects of his work, due, he said, to the excellent teachers he had there, and he immediately became the leader of his class in all subjects, a position he maintained throughout his high school years before graduating from Kendallville High School in 1911.

Before college Urey taught one year at the Noble County schools near Kendallville educating 25 students in various grades. Then he went off to Missoula, Montana where his mother, stepfather, brother, and sisters had already gone, and once again taught in small elementary schools. It was while teaching in a mining camp that the son of the family with which he was living decided to attend college, and this influenced Harold to do the same. He entered the University of Montana in Missoula in the autumn of 1914. By carrying a heavy schedule of courses he was able to complete his college education in three years with a straight A record, except in athletics. He did this in spite of being required by his financial situation to wait on tables in the girls’ dormitory and work one summer on the railroad being built there. Many years later in his Willard Gibbs Medal address he spoke warmly of the inspiration he received from the professors at the University of Montana and of the beginning of his interest in science due to their counseling advice, in particular the influence of A. W. Bray, professor of biology.

Under Bray’s guidance Harold majored in biology, and his first research effort was a study of the protozoa in a backwater of the Missoula River. His interest in the origins of life, a field in which he was to make a major contribution much later at the University of Chicago, originated with that earliest research. Bray also encouraged him to study chemistry, and he obtained a second major in that subject. World War I began as Urey entered the university, and at the time he completed his work there in 1917 the United States declared war. Urey earned his degree in Zoology in only 3 years! It was an accident that he entered the field of chemistry! He was urged by his professors to work in a chemical plant, chemists being badly needed at that time. During the rest of the war he worked at the Barrett Chemical Company in Philadelphia where he made TNT. In 1919 after the end of the war he returned to the University of Montana as instructor in chemistry.

An academic career required a doctorate, so in 1921 Urey enrolled in a PhD program at the University of California, Berkeley, where he studied thermodynamics under Gilbert N. Lewis. His initial attempt at a thesis was on the ionization of cesium vapor. He ran into difficulties, and an Indian physicist published a better paper on the same subject. Urey then wrote his thesis on the ionization states of an ideal gas, which was subsequently published in the Astrophysical Journal. After he received his PhD in 1923, Urey was awarded a fellowship by the American-Scandinavian Foundation to study at the Niels Bohr Institute in Copenhagen, where he met Werner Heisenberg, Hans Kramers, Wolfgang Pauli, Georg von Hevesy, and John Slater. At the conclusion of his stay, he traveled to Germany, where he met Albert Einstein andJames Franck.

On returning to the United States, Urey received an offer of a National Research Council fellowship to Harvard University, and also received an offer to be a research associate at Johns Hopkins University. He chose the latter. Before taking up the job, he traveled to Seattle, Washington, to visit his mother. On the way, he stopped byEverett, Washington, where he knew a woman called Kate Daum. Kate introduced Urey to her sister, Frieda. Urey and Frieda soon became engaged. They were married at her father's house in Lawrence, Kansas, in 1926. The couple had four children: Gertrude Bessie (Elisabeth), born in 1927; Frieda Rebecca, born in 1929; Mary Alice, born in 1934; and John Clayton Urey, born in 1939.

At Johns Hopkins, Urey and Arthur Ruark wrote Atoms, Quanta and Molecules (1930), one of the first English texts on quantum mechanics and its applications to atomic and molecular systems. In 1929, Urey became an associate professor of Chemistry at Columbia University, where his colleagues included Rudolph Schoenheimer, David Rittenberg, and T. I. Taylor. He initiated both experimental and theoretical research. In the former area his work was mainly in spectroscopy—ultraviolet spectra of triatomic molecules and vibrational spectroscopy. He and his student Charles Bradley measured the Raman spectrum of silico-chloroform, a tetrahedral molecule.

They found that none of the molecular force fields in use at the time could reproduce the spectra of tetrahedral molecules. They introduced a new force field, the Urey-Bradley field, which is an admixture of valence bond and central force fields. The Urey-Bradley field remains in use in the analysis of the vibrational spectra of tetrahedral molecules. Urey’s theoretical work at that time was directed to nuclear stability and the classification of atomic nuclei. In 1931 Urey had on the wall of his office a chart of atomic nuclei. On the ordinate his chart was labeled “protons”; on the abscissa he plotted “nuclear electrons.” This was prior to the discovery of the neutron. The number of nuclear electrons is the number of neutrons in the nucleus.

The atomic number or nuclear charge is the number of protons minus the number of nuclear electrons. For the light elements Urey’s chart showed the stable nuclei 1 1H, 4 2He, 6 3Li, 7 3Li, 9 4Be, 10 5B, and 11 5B. From nuclear systematics, Urey and others postulated the existence of 2 1H, 3 1H, and 5 2He. No isotopes of hydrogen or helium other than 1 1H and 4 2He were known in 1931. From atomic weight considerations, to be discussed below, it was estimated that, if a stable isotope of hydrogen of mass 2 existed, its natural abundance would be less than 1:30,000 parts of 1 1H. For the discovery of deuterium, Harold Urey received the Nobel Prize in chemistry in 1934. Urey was the third American to receive a Nobel Prize in chemistry. He was young in comparison with most Nobel laureates in chemistry prior to or since 1934.

Two papers written by Urey in 1938, “The Separation of

Isotopes” (1939,1) and “Separation of Isotopes” (1939,5),

throw light on the status of isotope separation at that time

and on Urey’s speculations about methods for separating

isotopes of the heavy elements. He proposed a countercurrent

flow centrifuge, designed to attain a number of stages

of separation in a single machine, thus reducing the number

of machines required in a cascade and the amount of

material circulated between machines. This led to his involvement with the Manhattan Project in Chicago where he led research in the development of the Atomic Bomb. His successes were incredible achievements that did not go unnoticed! He was also, sought out for his interests with the planetary spectrum and postulates about the Moon. He wrote books about it: "The Planets: Their Origin and Development," "The Planet Earth: A Scientific American Book," "The Origin of the Earth," and "Astrophysics III: The Solar System."

In later life, Urey helped develop the field of cosmochemistry and is credited with coining the term. His work on oxygen-18 led him to develop theories about the abundance of the chemical elements on earth, and of their abundance and evolution in the stars. In the late 1950s and early 1960s, space science became a topical field of research in the wake of the launch of Sputnik I. Urey helped persuade NASA to make unmanned probes to a moon a priority. When Apollo 11 returned moon rock samples from the moon, Urey examined them at the Lunar Receiving Laboratory. The samples supported Urey's contention that the moon and the Earth shared a common origin.

While at UCSD, Urey published 105 scientific papers, 47 of them about lunar topics. When asked why he continued to work so hard, he joked, "Well, you know I’m not on tenure anymore." Today, Harold C. Urey is known as one of the founders of NASA! He was sought after for his knowledge by John F. Kennedy, time and again, for the formation of the space agency alongside Dwight D. Eisenhower, and Wernher von Braun! He is honored by NASA with the Harold C. Urey Prize awarded each year by The Division for Planetary Sciences (DPS) of the American Astronomical Society at the Goddard Space Flight Center.

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